Radio signaling apparatus



Oct. 22, 1935.- G, W.- PET TENGILL ET AL 2,018,569

RAD IO SIGNALING APPARATUS Filed'June 17, 1933 5 Sheets-Sheet 1 V l/VVE/VTOEJ CarletonD is, GLDIZJB WBetterglL,

1935- s. w. PETTENGILL ET AL 2,018,569

RADIO S IGNALING APPARATUS Filed June 17, 1953 3 Sheets-Sheet 2 INVENTOES. CarZeZ'onDHaigvlS. George WBetZengzllL Oct- 22, 1935- G. w. PETTENGILL ET AL 6 RADIO SIGNALING APPARATUS Filed June 17, 1933 3 Sheets-Sheet 3 F455 mulllllllllmlw A I a klvvflvroles Jay " I r x T EIE flTTOEA/EK GarZewnDH I Georgn Patented Oct. 22, 1935 RADIO SIGNALING APPARATUS George W. Pettengill, Audubon, and Carleton D.

Haigls, Camden, N. 1., assignors to Radio Corporation of America, a corporation of Delaware Application June 17, 1933, Serial No. 676,246

18 Clalms. (01. 25018) Our invention relates to radio apparatus and particularly to combined transmitter and receiver apparatus for short wave transmission and reception. I

I An object of our invention is to provide a very small,readily portable, combined transmitter and receiver.

A further object of our invention is to provide an improved super-regenerative receiver for short wave reception.

A still further object of our invention is to provide means for automatically compensating the tuning when switching from transmitter to receiver.

In practicing our invention, we provide a pushpull oscillator which has a tuned grid circuit and a tuned plate circuit, this oscillator including suitable electric discharge devices or electronic tubes so connected through switching circuits.

tively as a speech amplifier or as an audio frei quency oscillator for transmitter operation, and as an audio frequency amplifier for receiving signals.

A second tube of the above amplifier may be utilized'selectively as a modulator for the transmittin'g operation, and as a second audio frequency amplifier for receiving signals.

There are, furthermore, input and output circuits provided for the amplifier in which impedance devices are connected each having a plurality of functions, and the switching means for the oscillator is arranged to include means for controlling the functioning of the amplifier as above described, whereby the apparatus. and electronic tubes required for a combined transmitter and receiver may be reduced to substantially a minimum, as is desirable in a portable signaling device.

Other features and advantages of our invention will appear from the following description taken in connection with the accompanying drawings in which: g

Figure 1 is a circuit diagram of a combined transmitter and receiver constructed in accordance with one embodiment of our invention;'

Figs. 2, 3, and 4 are circuit diagrams for the push-pull relation to each other,

apparatus shown in Fig. 1, for the three different switch positions;

Fig. 5 is a perspective view of the combined transmitter and receiver; and

Figs. 6 and 7 are views showing the switching 5 mechanism for automatically compensating the tuning when switching from transmitting to receiving.

Referring to Fig. 1, the apparatus includes an oscillator which comprises two electric discharge 10 devices or electronic tubes I and 3, connected in These tubes may be of any suitable type such as the usual triode type shown, and are provided with a tuned grid circuit 5 which consists of an inductance coil l shunted by two variable condensers 9 and II connected in series. The ends of the inductance coil 1 are connected to the control-grids of the tubes l and 3, respectively.

The condensers 9 and II have rotor plates which are mounted on a common shaft so that they are adjustable simultaneously. The rotor plates of condensers 9 and II, and therefore the mid-point of the tunedgrid circuit 5, are connected to the cathodes of the tubes l and 3 through suitable ground connections indicated inthe drawings by the conventional symbol and the reference numeral 6.

The tubes I and 3 are provided with a tuned plate circuit l3 which comprises an inductance coil l5 shunted by two variable condensers l1 and i9 connected in series. The ends of the inductance coil I 5 are connected to the plates of the tubes l and 3, respectively.

The rotors of the condensers I1 and I9 also are mounted on a common shaft so that they may be adjusted simultaneously, and these rotors also are connected to ground as indicated.

An antenna 2|, such as a dipole antenna, is coupled to the tuned plate circuit l3 by means of coils 23 placed in inductive relation to the'plate inductance coil IS. The antenna 2| may be con- .nected to the plate circuit l3 by capacitive coupling, if preferred. Particular attention is called to the fact that, in accordance with our inven- The switch 29, itself, is of conventional constructionand includes four blocks 3|, 33, 35, and

31 of insulating material, and a circular cam 39. when the cam 39 is in the central position shown 5 in the drawings, the switch 29 is in its receiving position andthe push-pull oscillator is connected to the audio frequency tubes 25 and 21 to form a super-regenerative receiver circuit. When the cam 39 is moved to the left, the blocks 3| and 35 1 are moved apart and the push-pull oscillator is so connected to the audio frequency tubes 25 and 21 that a telephone transmitter circuit employing Heising modulation is formed. When the cam 39 is moved to the right, the blocks 33 and 31 are moved apart and a telegraph circuit employing Heising modulation is formed.

Referring to Figs. 1 and 2, when the switch 29 is in the receiver position, the incoming modulated signal appears in the-plate circuit l3 of the 20 oscillator and is brought to the input circuit of an audio frequency amplifier comprising tubes 25 and 21 by means of a conductor 4| which connects the mid-point of the plate inductance coil |5 to the upper terminal of a primary winding 43 25 of an audio frequency transformer 45. In Fig. 1,

this connection may be traced from the midpoint of 'the inductance coil l5 to the lower switch arm on the block 3|, through a contact point and a continuation of conductor 4| to the 30 lower switch arm on the block 33, through a contact point and a continuation of conductor 4| to the upper end of the primary winding 43.

The audio frequency circuit is completed from the upper end of winding 43 through .the winding 35 to the positive terminal of the plate supply. The

primary winding 43 is shunted by a condenser 41 having a capacity large enough to by-pass the greater part of thesuper-audible frequency current appearing in the output of the push-pull 40 oscillator as a result of a super-regenerative quenching action hereinafter explained.

The grids of the oscillator tubes I and 3 are supplied with a biasing potential by means of a resistor 49 shunted by a condenser 5|, the circuit 45 through the resistor 53 being open when the switch 29 is in the receiving position. The grid biasing circuit may be traced from the mid-point of the grid inductance coil 1 through a resistor 55, the resistor 49 and a conductor 51 to the lower 50 terminal of the secondary winding 59 of the audio frequency transformer 45, and from there to the negative or C terminal of the source of biascontinuation of conductor 51 to the middle switch arm of the block 33, through a continuation of conductor 51 to the lower terminal of the sec- 60 ondary winding 59.

The values of the grid biasing resistors 49 and 55 and shunting condenser 5| are made such that a negative potential will build up periodi cally on the grldsof tubes I and 3 either to stop 65 the oscillations or to reduce their intensity. This periodic quenching action occurs at a superaudible frequency which may be of the order of 30,000 cycles per second. In one embodiment of our invention, resistors 49 and 55 were given 70 values of 25,000 ohms and 2000 ohms, respectively, and condenser 5| was given a value of .001 microfarad. In this same embodiment, resistor 53 was given a value of 5000 ohms.

It has been found that reception is materially 5 improved by utilizing the resistor 55 in series with the parallel connected units 49 and 5|. This is believed to be for the reason that, with the circuit employed, the charging rate of the condenser is determined largely by the value of resistor 55 while its discharging rate is deter- 5 mined by the value of resistor 49.

The circuit above-described impresses the demodulated signal upon the input circuit of the vacuum tube 21. The plate of the tube 21 is connected to the positive or +3 terminal of the plate supply source through the primary 5| of an audio frequency transformer 53. The secondary 65 of the transformer 83 is shunted by a high resistance unit 51 and connected to the input electrodes of the amplifier tube 25. The plate or tube 25 is connected to the plate supply through an inductance coil 99 which forms the primary of an audio frequency transformer 1| when the apparatus is being used as a receiver.

The secondary 13 of transformer 1| is shunted by a resistor 15 and the lower terminalconnected to ground. In Fig. 1 the connection between the upper end of resistor 15 and the upper end of secondary 13 may be traced from resistor 15 through conductor 11, through a switch contact point and the lower switch arm of block 35, through conductor 19, the lower switch arm of block 31, a contact point, and through a conductor 8| to secondary 13.

A telephone receiver jack 83 is connected across the resistor 15 by means of a connection to ground and a. connection through a conductor 85 to a variable tap 81 on the resistor 15. By adjusting the variable tap 81, the output volume for telephone reception through the jack 83, may be adjusted. The path of the conductor 85 may be traced from the receiver jack to a switch contact point and a switch arm 89 of the block 31, through a continuation of conductor 85, through a switch arm 9| of block 35, and through a contact point and a continuation of conductor 85 to the variable tap 81.

Although the scope of our invention is not to be restricted to any theory of operation advanced herein, it is our belief that the demodulation of the modulated carrier-wave impressed -upon the tuned plate circuit may be explained as follows: The modulated carrier is impressed upon the tuned grid circuit of the tubes and 3 through the grid plate capacity of the tubes. The system has negative resistance at least periodically and the signal builds up during these periods of negative resistance until it is of such amplitude that it is rectified by the tubes and 3 functioning in parallel. The periodicity of the 5 negative resistance isintroduced by the blocking action of the common grid condenser 5| and grid leak resistors and 49 and is influenced by the plate circuit impedance.

At any rate the system behaves as though the 5 thermionic tubes and 3 function in parallel to demodulate an incoming signal since the demodulated signal appears in the conductor 4| over which the plate potential is supplied to the tubes. It should be noted that as the oscillator approaches the blocked condition, the grids of both tubes become more negative whereby the total plate current of the tubes decreases. This, of course, differs from the operation of push-pull amplifier circuits in which the grid of one tube is made more positive at the same time that the grid of the other tube is made more negative whereby the output current remains substantially constant.

When the switch cat; as is moved to' the left case, the microphone jack 93 is connected to the second primary winding 95 of the audio frequency transformer 45. The upper terminal of the primary winding 95 is connected to the center contact member 91 of the jack 93 through a connection which may be traced from the upper terminal of the primary winding through a conductor 99, the upper contact point and upper switch arm of the block 3|, and through a continuation of the conductor 99 to the contact member 91 of the jack 93. The lower ter- 'minal of the primary winding 95 is connected to the ring contact member |I of the jack 93 through a connection which may-be traced from said lower terminal through conductors I03 and I05, a contact point and a switch arm I0'I- of the block 35, through a conductor I09 to the negative or -C bias supply terminal, and thence to ground since the positive side of the C bias supply source is grounded.

It will be noted that the connection to the upper terminal of the primary winding 43 has been broken at the bottom contact point and bottom switch arm of the block 3|. Also, the resistor I5 is no longer in shunt across the secondary winding I3 since the circuit has been opened at the lower contact point and lower switch arm of the block 35. It will also be noted'that the connecticmbetween the telephone receiver and the variable tap 81 has been broken by the opening of the circuit at the contact point and switch arm 9| of the block 35.- Although no greatamount of energy cannow be supplied to the telephone jack 83, it is connected in series with the secondary winding I3 through a high resistance unit I I1 so that the output of the transmitter maybe monitored.

As mentioned above, the connection from the -minal of the choke coil 69.

The quenching grid leak resistor 49 and grid condenser 5| are no longer in the oscillator circuit since theconnection through the conductor 51 has been broken at the switch arm 5 of the block 3|. The grids of the oscillator tubes I and 3 are now supplied with the proper bias for giving continuous sustained oscillations by means of a connection from the mid-point of the grid inductance coil 1 through the resistor 53 and through the upper contact point and upper switch arm of the block 35 to ground.

with the above described transmitter connections, it will be seen that theapparatus functions as a conventional transmitter having one audiofrequency amplifier stage, a modulator stage and a push-pull oscillator.

When the switch cam 39 is moved to the right,

the connections are changed to make the transmitte'r function as a modulated continuous-wave telegraph transmitter as shown in the simplified diagram in Fig. 4. In this switch position, the

connections are the same as those described above for the telephone transmitter, except for the connections of the audio-frequency tube 21.

The lower primary winding 43 of the audio frequency transformer 45 is still disconnected 5 from the transmitter circuit. The microphone jack 93 has been disconnected from the circuit since the connection throughconductor 99 is broken at the upper contact point and upper switch arm of the block 3|. The upper primary 1 winding 95 is now connected in afeed-back circuit in series with a transmitter key jack 'II'I, so that the tube 21 is caused to oscillate at an audio frequency when the key circuit is closed. This feed-back circuit may be traced from theplate of the tube' 21 through a conductor II9, the upper contact point and upper switch arm of the block 33, through a condenser HI and resistor I23 connected in series, through the pri" mary winding 95, through a conductor I03, a contact point and switch arm I25 of the block 31, and through conductor I2I to the center terminal or the key jack 1. The ring terminal of the key jack III is connected toground so thatwhen the key circuit is closed, the plate of 25 the tube 21 is connected to ground through the above-described circuit.

The telegraph circuit just described transmits a carrier wave which is modulated at the frequency of the audio frequency oscillator when the key circuit is closed.

One important feature of our invention is the use of a compensating condenser I3I which is automatically connected into the circuit when the switch is thrown from the receiving position to either one of the transmitting positions. We have found that when receiving fairly strong signals, it is necessary to tune the receiver oscillator to a frequency slightly different than the frequency of the 'incoming signal in order to 4 obtain best results. By connecting the small condenser |3I between one end of the grid inductance coil I and ground, when the switch 29 is thrown to a transmitting position, the apparatus is made to transmit at a slightly lower frequency than the frequency at which it is tuned for receiving. Thus, by. employing two similar transmitter-receiver units, the receiver will always oscillate at a slightly different frequency than the transmitter frequency. I

It may be noted that the use of compensating condenser I3| is desirable, aside from the fact that the receiver should be tuned slightly ofi resonance, since the load on the oscillator is increased when the switch is thrown to the trans mitting position. This increase in load tends to raise the frequency of the oscillator, but by switching in condenser |3| the frequency is actually lowered instead of being permitted to increase. 7

The mechanical details of the switching mechanism for the compensating condenser I3I, as well as those of the rest of the-transmitter-receiver, are shown in Figs. 5, 6, and 7.

Referring to Fig. 5, the complete transmitting f ported by a block of insulating material I35, while friction drive.

and n and the plate circuit c ndensers I1 and I9. I

The stators of condensers 9 and II are supthe rotors of these condensers are mounted upon a hollow shaft I31. The inductance coil 1 is mounted on top of the insulating block I35.

The stators of condensers I1 and I9 are supported by an insulating block I39. The rotors of these condensers are mounted upon a. shaft I which extends through the hollow shaft I31. The inductance coil I5 is mounted upon the insulatingblock I39, the coupling coil 23 being supported from insulating bushings I43 and held in inductive relation with the coil I5.

. The audio frequency tubes 25 and 21 are mounted in the rear of the casing.

The rotors of condensers 9 and II may be turned by a knob I45 on a panel I41, the knob being connected with the hollow shaft I31 through a friction drive. The position of the rotors of condensers 9 and II is indicated by the upper dial scale I49. The rotors of condensers I1 and I9 may be turned by the left hand knob I5I which is connected to the shaft I through a The position of these rotors is indicated by the lower scale I53.

The panel I41 also carries a voltmeter I55, 8. filament current adjustment I51, a volume control adjustment I59, a power switch I3I, and the handle I63 of the switch 29. Openings IS in the lower left-hand corner of the panel are provided for plugging in devices such as a telephone receiver, a key or a microphone for connection with the jacks 83, H1 and 93, respectively, which are associated with said openings at the rear of the panel.

The compensating condenser I3I comprises metal plates I and I61 insulated from each other and mounted upon an insulating support I69. Two arms "I of conducting material, which are connected to the plate I65, extend from the insulating support I69. A conducting pin I13 extends from the switch 29 and is positioned be tween the conducting arms I1 I. When the switch 29 is in its receiving position, the pin I13 is out of contact with both arms. When switch 29 is thrown to one transmitting position, it makes contact with one arm HI and when thrown to the other transmitting position, it makes contact with the other arm I1I. The compensating condenser I3I is connected into the oscillator circuit through the pin I13 as described, since this condenser is in the radio frequency circuit and therefore could not satisfactorily be switched in and. out of the circuit through the contacts on the switch 29.

The manner in which the pin I13 is operated by means of the switch 29 is shown in Figs. 6 and 7. The switch, itself,'is of conventional construction and comprises a supporting member I15, which has the handle I63 and cam 39 mounted thereon at one end. The insulating blocks 3|, 33, 35, and 31 through which the switch arms are moved, are mounted upon the spring members I11 with which the cam 39 makes contact. In order to simplify the drawings, the switch arms actuated by the insulating blocks have not been illustrated in Figs. 6 and 'l.

A lever I19 is pivotally mounted upon the switch supporting member' I15. The pin I13 extends upwardly from one end of lever I19. The other. end of the lever I19 is in the form of a yoke I8I, the arms of which extend on each side of the cam 39. Pins I93 extend downwardly from the ends in parallel with condenser II as indicated in Fig. 1.

If desired, the condenser I 3| may be replaced by an inductance coil coupled to coil 1, said inductance coil being short circuited by pin I13 when the apparatus is in the receiving position and open-circuited when in the transmitting position. By varying the amount of coupling between this coil and coil 1, it is possible to secure the proper degree of compensation.

In the operation of the system described, themductance I5 in the anode circuit of the oscillator devices I and 3 serves to transmit signals to the antenna system through suitable coupling means, and for incoming signals, serves as a coupling means together with the internal inner-electrode capacity of the devices I and 3 for the input or grid circuit in which the inductance 1 is included.

The devices I and 3 are in continuous oscillation at frequencies determined by the tuning condensers associated with the inductances 1 and I5, and as has hereinbefore been explained, the devices I and 3 operate as oscillators for signal transmission or as oscillating super-regenerative detectors for receiving signals.

The device 21 may operate as a speech amplifler for phone operation, in connection with a microphone or other suitable voice input device, not shown, when connected with thephone jack 23 and the primarywinding 95, which is of low impedance. The winding is also utilized for feed-back purposes for interrupted continuous telegraph wave transmission in connection with the plate lead I I9, whereby the device 21 may operate as an audio frequency. oscillator.

In the receiving position of the switch 29, the device 21, furthermore, operates as a first audio frequency amplifier. Therefore, it has three separate functions in the system described. The triple function obtainable in connection with the device 21 is due in part to the use in the input transformer 45 of a low impedance feed-back and microphone input winding 95, a high impedance input winding 43 for audio frequency signals, and a bypass'condenser 41, the latter providing a. shunt path for the quenching frequency employed for super-regeneration.

The device 25 may function as a modulator for transmitteroperation, or as the second audio frequency or output amplifier device for signal reception. The dual function of this device is in 00 part, made possible by the use of a suitable output transformer H which also may serve a dual purpose, as modulation choke coil for signal transmission and as an output, transformer for signal reception, as hereinbefore described. The primary winding 69 serves as the modulation choke winding and as such supplies anode current to the device 25 and the devices I and 3 for phone operation, through the lead 5.

In connection with Fig. 5 it may be pointed out that the tuning condensers are arranged in ganged relation with the inductances mounted directly thereon and above the condensers, making it possible to provide short leads to the output terminals at the top of the apparatus, whfle the wiring and whereby the leads to the tubes are relatively short, I

as is desirable in high frequency apparatus. The

tubes are, furthermore, easily removable and re-- placeable in the sockets, since they are by this construction; permitted to be mounted in a vertical position above the base-board. All of the control apparatus, including the meter, jacks and switches, are mounted on and supported by the front panel. The apparatus as a complete unit may therefore, be inserted in a suitable casing when in use and may easily be removed therefrom for inspection and adjustment.

, Because of the amplified circuits and reduction in the number of electrical discharge devices or electron tubes required, the apparatus may be made in a highly compact form as is indicated in the drawings, while, at the same time, the inductance windings are suitably spaced from the shielded side walls of the casing in which the apparatus is mounted in use.

From the foregoing description it will be apparent that various modifications may be made in our invention without departing from the spirit and scope thereof, and we desire, therefore, that only such limitations shall be placed thereon as are necessitated by the prior art and as set fort by the appended claims.

We claim as our invention:

1. The method of intelligence reception and transmission by the use of a plurality of electronic tubes disposed in balanced relation and having common grid and plate circuits, which includes causing said tubes to generate oscillations at a frequency of the order of that of the desired signal,

causing the amplitude of said oscillations to be limited periodically, impressing a signal wave upon said plate circuit to further modify said oscil-' lations, and de-modulating said modified oscillations by said tubes to produce audible signal indications in said plate circuit, and later utilizing said tubes for transmitting a carrier wave.

2. The method of intelligence reception and transmission through the use of a plurality of electronic tubes disposed in balanced relation and having common grid and plate circuits, which includes causing said tubes to generate oscillations, impressing signal waves upon said plate circuit, selectively causing said oscillations to be interrupted at' a predetermined rate to receive said signal waves, and impressing upon said plate circuit a modulation signal without interrupting said oscillations, for transmitting corresponding signal waves.

3. The method of selective intelligence transmission and reception through the use of a balanced electric discharge oscillator and an electric discharge amplifier, which includes selectively and for one condition of operation, causing said oscillator to operate as a signal detector with the oscillations periodically suppressed, applying the demodulated signal output therefrom to said amplifier and receiving the amplified output from said amplifier, for a second condition of operation, causing said oscillator to operate freely at a predetermined frequency, transferring said oscillations as signal energy to a utilization circuit, and supplying modulation signals to said oscillator through said amplifier, and for a third condition of operation, additionally providing signal regeneration in said amplifier and key controlling the regeneration to provide interrupted continuous wave signals. v

4. A combined radio transmitter and receiver comprising, in combination, a balanced electric' discharge oscillator having tapped grid and anode 6 circuit inductances, an audio frequency amplifier having an input coupling means and an output coupling means, and switching means for selectively connecting a tap on the grid inductance to biasing potential supply circuits, one of which 10 includes an impedance and a capacitor connected in parallel, and for connecting a tap on the anode inductance selectively to the input and to the output coupling means for said amplifier.

5. A combined radio transmitter and receiver comprising in combination, a balanced electric discharge oscillator having tapped grid and anode circuit inductances, an audio frequency amplifier having an input coupling means and an output coupling means, switching means for selectively connecting a tap on the grid inductance to the oscillator cathode directly and through a source of biasing potential including an impedance and a capacitor connected in parallel, and for connecting a tap on the anode inductance selectively to the input and the output coupling means for said amplifier, and means providing audio frequency regeneration through said amplifier input coupling means.

6. In a radio signaling system, the combination of a balanced electric discharge oscillator having an output anode circuit, and an electric discharge amplifier having an input circuit and an output anode circuit, and switching means interposed between said oscillator and said amplifier for connecting the output anode circuit of the oscillator selectively with the input circuit and with the output circuit of the amplifier.

7. In a radio signaling system, the combination of a balanced electric discharge oscillator having (0 an output anode circuit, and an electric discharge amplifier having an input circuit and an output anode circuit, switching means interposed between said oscillator and said amplifier for connecting the output anode circuit of the oscillator selectively with the input circuit and with the output circuit of the amplifier, means for causing regeneration in said amplifier, and a circuit for controlling the regeneration arranged to be connected therewith when said output circuits are connected together.

8. In a radio signaling system, the combination, of a balanced electric discharge oscillator having an output anode circuit, and an electric discharge amplifier having an input circuit and an output anode circuit, and switching means interposed between said oscillator and said amplifier for connecting the output anode circuit'of the oscillator selectively with the input circuit and with the output circuit of the amplifier, said amplifier 60 being adapted to transmit signals in the audio frequency range andhaving an input transformer provided with a relatively high impedance input winding and a relatively low impedance input winding, and having an output transformer pro- 05 viding a modulation choke coil common to both output circuits when said switching means is in a predetennined position. I

9. In a radio signaling system: the combination of a balanced electric discharge oscillator having an output anode circuit, and an electric discharge amplifier having an input circuit and an output anode circuit, switching means interposed between said oscillator and said amplifier for connecting the output anode circuit of the tectcr, means for decreasing the intensity of said i oscillator selectively with the input circuit and with the output circuit of the amplifier, said amplifier being adapted to transmit signals in the audio frequency range and having an input transformer provided with a relatively high impedance input winding and a relatively low impedance input winding, and having an output transformer providing a modulation choke coil common to both output circuits when said switching means is in a predetermined position, means connected across said high impedance winding for bypassing a super-regenerative quenching signal, and means controlled by said switching means for changing the operating frequency of said oscillator,

10. In combination, a super-regenerative receiver comprising a plurality of electronic tubes connected in balanced relation and having a common tuned grid circuit and a common tuned plate circuit whereby said tubes may'iointly be operated as an oscillating detector, means for altering the magnitude of said oscillations at a superaudible rate, means for impressing radio-frequency signals upon said tuned plate circuit, means for transferring audio-frequency signals from said tuned plate-circuit, and means for jointly utilizing said tubes as the oscillator of a transmitter.

11. In combination, a super-regenerative receiver comprising apair of electric discharge devices connected in push-pull, said devices having tuned grid circuits and tuned plate circuits whereby said devices may operate as an oscillating deoscillations periodically at a superaudible rate, means for impressing a signal modulated radiofrequency carrier wave'upon said plate circuits, whereby said carrier wave is demodulated to produce signals in said plate circuit, means for transferring said signals from said plate circuits, and means for utilizing said tube as the oscillator of a transmitter.

12. In combination, a super-regenerative receiver comprising a pair of electric discharge devices connected in balanced relation, means including a tuned grid circuit for said tubes and a tuned plate circuit for making said devices operate as an oscillating detector, means for decreasing tunable grid circuit and a common tunable plate circuit, means enabling said tubes to generate oscillations, means for impressing a modulated signal wave directly upon the plate circuit of .said tubes in balanced relation, means for providing a discontinuous grid leakage from said tubes, means for transferring audio frequency signals from said plate circuit, and means for utilizing said tubes as the oscillator of a transmitter.

14. In combination, a signal receiving apparatus comprising a plurality of electronic tubes disposed in balanced relation and having a common, tunable grid circuit and a common tunable plate circuit, means enabling said tubes to generate oscillations, means for impressing a modulated signal wave directly upon the plate circuit of said M tubes in balanced relation, means for providing a discontinuous grid leak from said tubes, said last means including a resistor shunted by a condenser and a resistor connected in series with said shunted resistor, means for transferring audio- 1! frequency signals from said plate circuit, and means for utilizing said tubes as the oscillator of a transmitter.

15. In combination, an oscillator comprising a pair of electronic tubes connected-in balanced re- 2( lation to oscillate at a high frequency, said tubes havinga tuned grid circuit and a tuned plate circuitQan antenna, means for coupling said antenna to said plate circuit, a modulating circuit, a receiver circuit, means for selectively connecting 2! said modulating circuit and said receiver circuit with said plate circuit, and means for decreasing the intensity of.said oscillations periodically at a superaudible rate when said receiver circuit is connected to said plate circuit. v 3( 16. In combination, an oscillator having a grid circuit and a plate circuit, an antenna coupled to said plate circuit, an electric discharge amplifier device having an input circuit and an output circuit, an audio-frequency transformer in said 35 output circuit, switching means having a receiving position and a transmitting position, circuit means for coupling said plate circuit to said input circuit and for establishing a telephone receiver connection with the secondary of said trans- 4t former when said switching mechanism is in said receiving position, and circuit means for establishing a connection between said plate circuit and the primary of said audio-frequency transformer when said switching mechanism is in said .45 transmitting position.

17. In combination, an oscillator, a modulating circuit, a receiver circuit, switching means for selectively connecting said circuits to said oscillator, and means for changing the frequency of op- 66 eration of saidoscillator in response to the-0peration of said switching means.

18. In combination, an oscillator, a modulating circuit, a receiving circuit, switching means for selectively connecting said circuits to said oscilla- 5! tor, means'for causing the oscillations of said oscillator to be reduced in intensity periodically at a superaudible frequency when said receiving circuit is connected to said oscillator, and means for changing the tuningof said oscillator in response to the operation of said switching means.

GEORGE W. PE'I'IENGIIL. CARLETON D. HAIGis. 

